Use Map.forEach instead of manual Map.Entry iteration wherever possible

Issue: SPR-16646

spring-beans/src/main/java/org/springframework/beans/PropertyEditorRegistrySupport.java

@@ -466,9 +466,7 @@ public class PropertyEditorRegistrySupport implements PropertyEditorRegistry {
 			this.customEditors.forEach(target::registerCustomEditor);
 		}
 		if (this.customEditorsForPath != null) {
-			for (Map.Entry<String, CustomEditorHolder> entry : this.customEditorsForPath.entrySet()) {
-				String editorPath = entry.getKey();
-				CustomEditorHolder editorHolder = entry.getValue();
+			this.customEditorsForPath.forEach((editorPath, editorHolder) -> {
 				if (nestedProperty != null) {
 					int pos = PropertyAccessorUtils.getFirstNestedPropertySeparatorIndex(editorPath);
 					if (pos != -1) {
@@ -484,7 +482,7 @@ public class PropertyEditorRegistrySupport implements PropertyEditorRegistry {
 					target.registerCustomEditor(
 							editorHolder.getRegisteredType(), editorPath, editorHolder.getPropertyEditor());
 				}
-			}
+			});
 		}
 	}
 

spring-beans/src/main/java/org/springframework/beans/factory/config/CustomScopeConfigurer.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -97,9 +97,7 @@ public class CustomScopeConfigurer implements BeanFactoryPostProcessor, BeanClas
 	@Override
 	public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
 		if (this.scopes != null) {
-			for (Map.Entry<String, Object> entry : this.scopes.entrySet()) {
-				String scopeKey = entry.getKey();
-				Object value = entry.getValue();
+			this.scopes.forEach((scopeKey, value) -> {
 				if (value instanceof Scope) {
 					beanFactory.registerScope(scopeKey, (Scope) value);
 				}
@@ -118,7 +116,7 @@ public class CustomScopeConfigurer implements BeanFactoryPostProcessor, BeanClas
 							scopeKey + "] is not an instance of required type [" + Scope.class.getName() +
 							"] or a corresponding Class or String value indicating a Scope implementation");
 				}
-			}
+			});
 		}
 	}
 

spring-beans/src/main/java/org/springframework/beans/factory/config/YamlProcessor.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -25,7 +25,6 @@ import java.util.Collections;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
-import java.util.Map.Entry;
 import java.util.Properties;
 import java.util.Set;
 
@@ -272,8 +271,7 @@ public abstract class YamlProcessor {
 	}
 
 	private void buildFlattenedMap(Map<String, Object> result, Map<String, Object> source, @Nullable String path) {
-		for (Entry<String, Object> entry : source.entrySet()) {
-			String key = entry.getKey();
+		source.forEach((key, value) -> {
 			if (StringUtils.hasText(path)) {
 				if (key.startsWith("[")) {
 					key = path + key;
@@ -282,7 +280,6 @@ public abstract class YamlProcessor {
 					key = path + '.' + key;
 				}
 			}
-			Object value = entry.getValue();
 			if (value instanceof String) {
 				result.put(key, value);
 			}
@@ -305,7 +302,7 @@ public abstract class YamlProcessor {
 			else {
 				result.put(key, (value != null ? value : ""));
 			}
-		}
+		});
 	}
 
 

spring-beans/src/main/java/org/springframework/beans/factory/support/BeanDefinitionValueResolver.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -421,12 +421,11 @@ class BeanDefinitionValueResolver {
 	 */
 	private Map<?, ?> resolveManagedMap(Object argName, Map<?, ?> mm) {
 		Map<Object, Object> resolved = new LinkedHashMap<>(mm.size());
-		for (Map.Entry<?, ?> entry : mm.entrySet()) {
-			Object resolvedKey = resolveValueIfNecessary(argName, entry.getKey());
-			Object resolvedValue = resolveValueIfNecessary(
-					new KeyedArgName(argName, entry.getKey()), entry.getValue());
+		mm.forEach((key, value) -> {
+			Object resolvedKey = resolveValueIfNecessary(argName, key);
+			Object resolvedValue = resolveValueIfNecessary(new KeyedArgName(argName, key), value);
 			resolved.put(resolvedKey, resolvedValue);
-		}
+		});
 		return resolved;
 	}
 

spring-context/src/main/java/org/springframework/context/annotation/ConfigurationClassBeanDefinitionReader.java

@@ -315,10 +315,7 @@ class ConfigurationClassBeanDefinitionReader {
 
 		Map<Class<?>, BeanDefinitionReader> readerInstanceCache = new HashMap<>();
 
-		for (Map.Entry<String, Class<? extends BeanDefinitionReader>> entry : importedResources.entrySet()) {
-			String resource = entry.getKey();
-			Class<? extends BeanDefinitionReader> readerClass = entry.getValue();
-
+		importedResources.forEach((resource, readerClass) -> {
 			// Default reader selection necessary?
 			if (BeanDefinitionReader.class == readerClass) {
 				if (StringUtils.endsWithIgnoreCase(resource, ".groovy")) {
@@ -352,7 +349,7 @@ class ConfigurationClassBeanDefinitionReader {
 
 			// TODO SPR-6310: qualify relative path locations as done in AbstractContextLoader.modifyLocations
 			reader.loadBeanDefinitions(resource);
-		}
+		});
 	}
 
 	private void loadBeanDefinitionsFromRegistrars(Map<ImportBeanDefinitionRegistrar, AnnotationMetadata> registrars) {

spring-core/src/main/java/org/springframework/core/Constants.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -215,11 +215,11 @@ public class Constants {
 	public Set<Object> getValues(@Nullable String namePrefix) {
 		String prefixToUse = (namePrefix != null ? namePrefix.trim().toUpperCase(Locale.ENGLISH) : "");
 		Set<Object> values = new HashSet<>();
-		for (String code : this.fieldCache.keySet()) {
+		this.fieldCache.forEach((code, value) -> {
 			if (code.startsWith(prefixToUse)) {
-				values.add(this.fieldCache.get(code));
+				values.add(value);
 			}
-		}
+		});
 		return values;
 	}
 
@@ -247,11 +247,11 @@ public class Constants {
 	public Set<Object> getValuesForSuffix(@Nullable String nameSuffix) {
 		String suffixToUse = (nameSuffix != null ? nameSuffix.trim().toUpperCase(Locale.ENGLISH) : "");
 		Set<Object> values = new HashSet<>();
-		for (String code : this.fieldCache.keySet()) {
+		this.fieldCache.forEach((code, value) -> {
 			if (code.endsWith(suffixToUse)) {
-				values.add(this.fieldCache.get(code));
+				values.add(value);
 			}
-		}
+		});
 		return values;
 	}
 

spring-core/src/main/java/org/springframework/core/SimpleAliasRegistry.java

@@ -141,8 +141,7 @@ public class SimpleAliasRegistry implements AliasRegistry {
 		Assert.notNull(valueResolver, "StringValueResolver must not be null");
 		synchronized (this.aliasMap) {
 			Map<String, String> aliasCopy = new HashMap<>(this.aliasMap);
-			for (String alias : aliasCopy.keySet()) {
-				String registeredName = aliasCopy.get(alias);
+			aliasCopy.forEach((alias, registeredName) -> {
 				String resolvedAlias = valueResolver.resolveStringValue(alias);
 				String resolvedName = valueResolver.resolveStringValue(registeredName);
 				if (resolvedAlias == null || resolvedName == null || resolvedAlias.equals(resolvedName)) {
@@ -154,7 +153,7 @@ public class SimpleAliasRegistry implements AliasRegistry {
 						if (existingName.equals(resolvedName)) {
 							// Pointing to existing alias - just remove placeholder
 							this.aliasMap.remove(alias);
-							break;
+							return;
 						}
 						throw new IllegalStateException(
 								"Cannot register resolved alias '" + resolvedAlias + "' (original: '" + alias +
@@ -168,7 +167,7 @@ public class SimpleAliasRegistry implements AliasRegistry {
 				else if (!registeredName.equals(resolvedName)) {
 					this.aliasMap.put(alias, resolvedName);
 				}
-			}
+			});
 		}
 	}
 

spring-core/src/main/java/org/springframework/core/annotation/AnnotationUtils.java

@@ -1246,21 +1246,18 @@ public abstract class AnnotationUtils {
 		if (!attributes.validated) {
 			// Validate @AliasFor configuration
 			Map<String, List<String>> aliasMap = getAttributeAliasMap(annotationType);
-			for (String attributeName : aliasMap.keySet()) {
+			aliasMap.forEach((attributeName, aliasedAttributeNames) -> {
 				if (valuesAlreadyReplaced.contains(attributeName)) {
-					continue;
+					return;
 				}
 				Object value = attributes.get(attributeName);
 				boolean valuePresent = (value != null && !(value instanceof DefaultValueHolder));
-
-				for (String aliasedAttributeName : aliasMap.get(attributeName)) {
+				for (String aliasedAttributeName : aliasedAttributeNames) {
 					if (valuesAlreadyReplaced.contains(aliasedAttributeName)) {
 						continue;
 					}
-
 					Object aliasedValue = attributes.get(aliasedAttributeName);
 					boolean aliasPresent = (aliasedValue != null && !(aliasedValue instanceof DefaultValueHolder));
-
 					// Something to validate or replace with an alias?
 					if (valuePresent || aliasPresent) {
 						if (valuePresent && aliasPresent) {
@@ -1290,7 +1287,7 @@ public abstract class AnnotationUtils {
 						}
 					}
 				}
-			}
+			});
 			attributes.validated = true;
 		}
 

spring-core/src/main/java/org/springframework/core/io/support/SpringFactoriesLoader.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -121,8 +121,10 @@ public abstract class SpringFactoriesLoader {
 
 	private static Map<String, List<String>> loadSpringFactories(@Nullable ClassLoader classLoader) {
 		MultiValueMap<String, String> result = cache.get(classLoader);
-		if (result != null)
+		if (result != null) {
 			return result;
+		}
+
 		try {
 			Enumeration<URL> urls = (classLoader != null ?
 					classLoader.getResources(FACTORIES_RESOURCE_LOCATION) :

spring-core/src/main/java/org/springframework/util/LinkedMultiValueMap.java

@@ -196,8 +196,7 @@ public class LinkedMultiValueMap<K, V> implements MultiValueMap<K, V>, Serializa
 	 */
 	public LinkedMultiValueMap<K, V> deepCopy() {
 		LinkedMultiValueMap<K, V> copy = new LinkedMultiValueMap<>(this.targetMap.size());
-		this.targetMap.forEach((k, v) -> copy.put(k, new LinkedList<>(v)));
-		
+		this.targetMap.forEach((key, value) -> copy.put(key, new LinkedList<>(value)));
 		return copy;
 	}
 

spring-core/src/main/java/org/springframework/util/MimeType.java

@@ -409,7 +409,8 @@ public class MimeType implements Comparable<MimeType>, Serializable {
 			return false;
 		}
 
-		for (String key : this.parameters.keySet()) {
+		for (Map.Entry<String, String> entry : this.parameters.entrySet()) {
+			String key = entry.getKey();
 			if (!other.parameters.containsKey(key)) {
 				return false;
 			}
@@ -418,7 +419,7 @@ public class MimeType implements Comparable<MimeType>, Serializable {
 					return false;
 				}
 			}
-			else if (!ObjectUtils.nullSafeEquals(this.parameters.get(key), other.parameters.get(key))) {
+			else if (!ObjectUtils.nullSafeEquals(entry.getValue(), other.parameters.get(key))) {
 				return false;
 			}
 		}

spring-jdbc/src/main/java/org/springframework/jdbc/core/metadata/CallMetaDataContext.java

@@ -563,14 +563,14 @@ public class CallMetaDataContext {
 		}
 
 		Map<String, Object> matchedParameters = new HashMap<>(inParameters.size());
-		for (String parameterName : inParameters.keySet()) {
+		inParameters.forEach((parameterName, parameterValue) -> {
 			String parameterNameToMatch = provider.parameterNameToUse(parameterName);
 			String callParameterName = callParameterNames.get(lowerCase(parameterNameToMatch));
 			if (callParameterName == null) {
 				if (logger.isDebugEnabled()) {
-					Object value = inParameters.get(parameterName);
+					Object value = parameterValue;
 					if (value instanceof SqlParameterValue) {
-						value = ((SqlParameterValue)value).getValue();
+						value = ((SqlParameterValue) value).getValue();
 					}
 					if (value != null) {
 						logger.debug("Unable to locate the corresponding IN or IN-OUT parameter for \"" +
@@ -579,9 +579,9 @@ public class CallMetaDataContext {
 				}
 			}
 			else {
-				matchedParameters.put(callParameterName, inParameters.get(parameterName));
+				matchedParameters.put(callParameterName, parameterValue);
 			}
-		}
+		});
 
 		if (matchedParameters.size() < callParameterNames.size()) {
 			for (String parameterName : callParameterNames.keySet()) {

spring-jdbc/src/main/java/org/springframework/jdbc/core/metadata/TableMetaDataContext.java

@@ -244,13 +244,21 @@ public class TableMetaDataContext {
 	 * @param inParameters the parameter names and values
 	 */
 	public List<Object> matchInParameterValuesWithInsertColumns(Map<String, ?> inParameters) {
-		List<Object> values = new ArrayList<>();
-		Map<String, Object> source = new LinkedHashMap<>(inParameters.size());
-		for (String key : inParameters.keySet()) {
-			source.put(key.toLowerCase(), inParameters.get(key));
-		}
+		List<Object> values = new ArrayList<>(inParameters.size());
 		for (String column : this.tableColumns) {
-			values.add(source.get(column.toLowerCase()));
+			Object value = inParameters.get(column);
+			if (value == null) {
+				value = inParameters.get(column.toLowerCase());
+				if (value == null) {
+					for (Map.Entry<String, ?> entry : inParameters.entrySet()) {
+						if (column.equalsIgnoreCase(entry.getKey())) {
+							value = entry.getValue();
+							// TODO: break;
+						}
+					}
+				}
+			}
+			values.add(value);
 		}
 		return values;
 	}

spring-jdbc/src/main/java/org/springframework/jdbc/core/simple/AbstractJdbcCall.java

@@ -314,11 +314,9 @@ public abstract class AbstractJdbcCall {
 		this.callMetaDataContext.initializeMetaData(dataSource);
 
 		// Iterate over the declared RowMappers and register the corresponding SqlParameter
-		for (Map.Entry<String, RowMapper<?>> entry : this.declaredRowMappers.entrySet()) {
-			SqlParameter resultSetParameter =
-					this.callMetaDataContext.createReturnResultSetParameter(entry.getKey(), entry.getValue());
-			this.declaredParameters.add(resultSetParameter);
-		}
+		this.declaredRowMappers.forEach((key, value) -> {
+			this.declaredParameters.add(this.callMetaDataContext.createReturnResultSetParameter(key, value));
+		});
 		this.callMetaDataContext.processParameters(this.declaredParameters);
 
 		this.callString = this.callMetaDataContext.createCallString();
@@ -326,8 +324,8 @@ public abstract class AbstractJdbcCall {
 			logger.debug("Compiled stored procedure. Call string is [" + this.callString + "]");
 		}
 
-		this.callableStatementFactory =
-				new CallableStatementCreatorFactory(this.callString, this.callMetaDataContext.getCallParameters());
+		this.callableStatementFactory = new CallableStatementCreatorFactory(
+				this.callString, this.callMetaDataContext.getCallParameters());
 
 		onCompileInternal();
 	}

spring-jdbc/src/main/java/org/springframework/jdbc/support/CustomSQLExceptionTranslatorRegistrar.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -22,8 +22,7 @@ import java.util.Map;
 import org.springframework.beans.factory.InitializingBean;
 
 /**
- * Registry for registering custom {@link org.springframework.jdbc.support.SQLExceptionTranslator}
- * instances for specific databases.
+ * Registry for custom {@link SQLExceptionTranslator} instances for specific databases.
  *
  * @author Thomas Risberg
  * @since 3.1.1
@@ -50,9 +49,8 @@ public class CustomSQLExceptionTranslatorRegistrar implements InitializingBean {
 
 	@Override
 	public void afterPropertiesSet() {
-		for (String dbName : this.translators.keySet()) {
-			CustomSQLExceptionTranslatorRegistry.getInstance().registerTranslator(dbName, this.translators.get(dbName));
-		}
+		this.translators.forEach((dbName, translator) ->
+				CustomSQLExceptionTranslatorRegistry.getInstance().registerTranslator(dbName, translator));
 	}
 
 }

spring-jms/src/main/java/org/springframework/jms/support/converter/SimpleMessageConverter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -147,11 +147,12 @@ public class SimpleMessageConverter implements MessageConverter {
 	protected MapMessage createMessageForMap(Map<?, ?> map, Session session) throws JMSException {
 		MapMessage message = session.createMapMessage();
 		for (Map.Entry<?, ?> entry : map.entrySet()) {
-			if (!(entry.getKey() instanceof String)) {
+			Object key = entry.getKey();
+			if (!(key instanceof String)) {
 				throw new MessageConversionException("Cannot convert non-String key of type [" +
-						ObjectUtils.nullSafeClassName(entry.getKey()) + "] to JMS MapMessage entry");
+						ObjectUtils.nullSafeClassName(key) + "] to JMS MapMessage entry");
 			}
-			message.setObject((String) entry.getKey(), entry.getValue());
+			message.setObject((String) key, entry.getValue());
 		}
 		return message;
 	}

spring-messaging/src/main/java/org/springframework/messaging/simp/SimpAttributes.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2014 the original author or authors.
+ * Copyright 2002-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -168,16 +168,16 @@ public class SimpAttributes {
 	}
 
 	private void executeDestructionCallbacks() {
-		for (Map.Entry<String, Object> entry : this.attributes.entrySet()) {
-			if (entry.getKey().startsWith(DESTRUCTION_CALLBACK_NAME_PREFIX)) {
+		this.attributes.forEach((key, value) -> {
+			if (key.startsWith(DESTRUCTION_CALLBACK_NAME_PREFIX)) {
 				try {
-					((Runnable) entry.getValue()).run();
+					((Runnable) value).run();
 				}
 				catch (Throwable ex) {
 					logger.error("Uncaught error in session attribute destruction callback", ex);
 				}
 			}
-		}
+		});
 	}
 
 

spring-messaging/src/main/java/org/springframework/messaging/simp/SimpMessagingTemplate.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -263,10 +263,7 @@ public class SimpMessagingTemplate extends AbstractMessageSendingTemplate<String
 
 		SimpMessageHeaderAccessor headerAccessor = SimpMessageHeaderAccessor.create(SimpMessageType.MESSAGE);
 		initHeaders(headerAccessor);
-		for (Map.Entry<String, Object> headerEntry : headers.entrySet()) {
-			Object value = headerEntry.getValue();
-			headerAccessor.setNativeHeader(headerEntry.getKey(), (value != null ? value.toString() : null));
-		}
+		headers.forEach((key, value) -> headerAccessor.setNativeHeader(key, (value != null ? value.toString() : null)));
 		return headerAccessor.getMessageHeaders();
 	}
 

spring-messaging/src/main/java/org/springframework/messaging/simp/broker/DefaultSubscriptionRegistry.java

@@ -270,8 +270,8 @@ public class DefaultSubscriptionRegistry extends AbstractSubscriptionRegistry {
 					for (SessionSubscriptionInfo info : subscriptionRegistry.getAllSubscriptions()) {
 						for (String destinationPattern : info.getDestinations()) {
 							if (getPathMatcher().match(destinationPattern, destination)) {
-								for (Subscription subscription : info.getSubscriptions(destinationPattern)) {
-									result.add(info.sessionId, subscription.getId());
+								for (Subscription sub : info.getSubscriptions(destinationPattern)) {
+									result.add(info.sessionId, sub.getId());
 								}
 							}
 						}
@@ -287,27 +287,23 @@ public class DefaultSubscriptionRegistry extends AbstractSubscriptionRegistry {
 
 		public void updateAfterNewSubscription(String destination, String sessionId, String subsId) {
 			synchronized (this.updateCache) {
-				for (Map.Entry<String, LinkedMultiValueMap<String, String>> entry : this.updateCache.entrySet()) {
-					String cachedDestination = entry.getKey();
+				this.updateCache.forEach((cachedDestination, subscriptions) -> {
 					if (getPathMatcher().match(destination, cachedDestination)) {
-						LinkedMultiValueMap<String, String> subs = entry.getValue();
 						// Subscription id's may also be populated via getSubscriptions()
-						List<String> subsForSession = subs.get(sessionId);
+						List<String> subsForSession = subscriptions.get(sessionId);
 						if (subsForSession == null || !subsForSession.contains(subsId)) {
-							subs.add(sessionId, subsId);
-							this.accessCache.put(cachedDestination, subs.deepCopy());
+							subscriptions.add(sessionId, subsId);
+							this.accessCache.put(cachedDestination, subscriptions.deepCopy());
 						}
 					}
-				}
+				});
 			}
 		}
 
 		public void updateAfterRemovedSubscription(String sessionId, String subsId) {
 			synchronized (this.updateCache) {
 				Set<String> destinationsToRemove = new HashSet<>();
-				for (Map.Entry<String, LinkedMultiValueMap<String, String>> entry : this.updateCache.entrySet()) {
-					String destination = entry.getKey();
-					LinkedMultiValueMap<String, String> sessionMap = entry.getValue();
+				this.updateCache.forEach((destination, sessionMap) -> {
 					List<String> subscriptions = sessionMap.get(sessionId);
 					if (subscriptions != null) {
 						subscriptions.remove(subsId);
@@ -321,7 +317,7 @@ public class DefaultSubscriptionRegistry extends AbstractSubscriptionRegistry {
 							this.accessCache.put(destination, sessionMap.deepCopy());
 						}
 					}
-				}
+				});
 				for (String destination : destinationsToRemove) {
 					this.updateCache.remove(destination);
 					this.accessCache.remove(destination);
@@ -332,9 +328,7 @@ public class DefaultSubscriptionRegistry extends AbstractSubscriptionRegistry {
 		public void updateAfterRemovedSession(SessionSubscriptionInfo info) {
 			synchronized (this.updateCache) {
 				Set<String> destinationsToRemove = new HashSet<>();
-				for (Map.Entry<String, LinkedMultiValueMap<String, String>> entry : this.updateCache.entrySet()) {
-					String destination = entry.getKey();
-					LinkedMultiValueMap<String, String> sessionMap = entry.getValue();
+				this.updateCache.forEach((destination, sessionMap) -> {
 					if (sessionMap.remove(info.getSessionId()) != null) {
 						if (sessionMap.isEmpty()) {
 							destinationsToRemove.add(destination);
@@ -343,7 +337,7 @@ public class DefaultSubscriptionRegistry extends AbstractSubscriptionRegistry {
 							this.accessCache.put(destination, sessionMap.deepCopy());
 						}
 					}
-				}
+				});
 				for (String destination : destinationsToRemove) {
 					this.updateCache.remove(destination);
 					this.accessCache.remove(destination);
@@ -433,13 +427,9 @@ public class DefaultSubscriptionRegistry extends AbstractSubscriptionRegistry {
 		public Subscription getSubscription(String subscriptionId) {
 			for (Map.Entry<String, Set<DefaultSubscriptionRegistry.Subscription>> destinationEntry :
 					this.destinationLookup.entrySet()) {
-
-				Set<Subscription> subs = destinationEntry.getValue();
-				if (subs != null) {
-					for (Subscription sub : subs) {
-						if (sub.getId().equalsIgnoreCase(subscriptionId)) {
-							return sub;
-						}
+				for (Subscription sub : destinationEntry.getValue()) {
+					if (sub.getId().equalsIgnoreCase(subscriptionId)) {
+						return sub;
 					}
 				}
 			}

spring-messaging/src/main/java/org/springframework/messaging/simp/broker/SimpleBrokerMessageHandler.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -19,7 +19,6 @@ package org.springframework.messaging.simp.broker;
 import java.security.Principal;
 import java.util.Arrays;
 import java.util.Collection;
-import java.util.List;
 import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ScheduledFuture;
@@ -352,11 +351,11 @@ public class SimpleBrokerMessageHandler extends AbstractBrokerMessageHandler {
 			logger.debug("Broadcasting to " + subscriptions.size() + " sessions.");
 		}
 		long now = System.currentTimeMillis();
-		for (Map.Entry<String, List<String>> subscriptionEntry : subscriptions.entrySet()) {
-			for (String subscriptionId : subscriptionEntry.getValue()) {
+		subscriptions.forEach((sessionId, subscriptionIds) -> {
+			for (String subscriptionId : subscriptionIds) {
 				SimpMessageHeaderAccessor headerAccessor = SimpMessageHeaderAccessor.create(SimpMessageType.MESSAGE);
 				initHeaders(headerAccessor);
-				headerAccessor.setSessionId(subscriptionEntry.getKey());
+				headerAccessor.setSessionId(sessionId);
 				headerAccessor.setSubscriptionId(subscriptionId);
 				headerAccessor.copyHeadersIfAbsent(message.getHeaders());
 				Object payload = message.getPayload();
@@ -370,13 +369,13 @@ public class SimpleBrokerMessageHandler extends AbstractBrokerMessageHandler {
 					}
 				}
 				finally {
-					SessionInfo info = this.sessions.get(subscriptionEntry.getKey());
+					SessionInfo info = this.sessions.get(sessionId);
 					if (info != null) {
 						info.setLastWriteTime(now);
 					}
 				}
 			}
-		}
+		});
 	}
 
 	@Override

spring-messaging/src/main/java/org/springframework/messaging/simp/broker/SubscriptionRegistry.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2015 the original author or authors.
+ * Copyright 2002-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -45,11 +45,11 @@ public interface SubscriptionRegistry {
 	void unregisterAllSubscriptions(String sessionId);
 
 	/**
-	 * Find all subscriptions that should receive the given message. The map
-	 * returned is safe to iterate and will never be modified.
+	 * Find all subscriptions that should receive the given message.
+	 * The map returned is safe to iterate and will never be modified.
 	 * @param message the message
-	 * @return a {@code MultiValueMap} with sessionId-subscriptionId pairs,
-	 * possibly empty.
+	 * @return a {@code MultiValueMap} with sessionId-subscriptionId pairs
+	 * (possibly empty)
 	 */
 	MultiValueMap<String, String> findSubscriptions(Message<?> message);
 

spring-web/src/main/java/org/springframework/http/HttpHeaders.java

@@ -416,12 +416,8 @@ public class HttpHeaders implements MultiValueMap<String, String>, Serializable
 	private HttpHeaders(Map<String, List<String>> headers, boolean readOnly) {
 		Assert.notNull(headers, "'headers' must not be null");
 		if (readOnly) {
-			Map<String, List<String>> map =
-					new LinkedCaseInsensitiveMap<>(headers.size(), Locale.ENGLISH);
-			for (Entry<String, List<String>> entry : headers.entrySet()) {
-				List<String> values = Collections.unmodifiableList(entry.getValue());
-				map.put(entry.getKey(), values);
-			}
+			Map<String, List<String>> map = new LinkedCaseInsensitiveMap<>(headers.size(), Locale.ENGLISH);
+			headers.forEach((key, valueList) -> map.put(key, Collections.unmodifiableList(valueList)));
 			this.headers = Collections.unmodifiableMap(map);
 		}
 		else {
@@ -1438,9 +1434,7 @@ public class HttpHeaders implements MultiValueMap<String, String>, Serializable
 
 	@Override
 	public void addAll(MultiValueMap<String, String> values) {
-		for (Entry<String, List<String>> entry : values.entrySet()) {
-			addAll(entry.getKey(), entry.getValue());
-		}
+		values.forEach(this::addAll);
 	}
 
 	/**
@@ -1460,17 +1454,13 @@ public class HttpHeaders implements MultiValueMap<String, String>, Serializable
 
 	@Override
 	public void setAll(Map<String, String> values) {
-		for (Entry<String, String> entry : values.entrySet()) {
-			set(entry.getKey(), entry.getValue());
-		}
+		values.forEach(this::set);
 	}
 
 	@Override
 	public Map<String, String> toSingleValueMap() {
 		LinkedHashMap<String, String> singleValueMap = new LinkedHashMap<>(this.headers.size());
-		for (Entry<String, List<String>> entry : this.headers.entrySet()) {
-			singleValueMap.put(entry.getKey(), entry.getValue().get(0));
-		}
+		this.headers.forEach((key, valueList) -> singleValueMap.put(key, valueList.get(0)));
 		return singleValueMap;
 	}
 

spring-web/src/main/java/org/springframework/http/client/HttpComponentsClientHttpRequest.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -18,8 +18,6 @@ package org.springframework.http.client;
 
 import java.io.IOException;
 import java.net.URI;
-import java.util.List;
-import java.util.Map;
 
 import org.apache.http.HttpEntity;
 import org.apache.http.HttpEntityEnclosingRequest;
@@ -97,19 +95,18 @@ final class HttpComponentsClientHttpRequest extends AbstractBufferingClientHttpR
 	 * @param headers the headers to add
 	 */
 	static void addHeaders(HttpUriRequest httpRequest, HttpHeaders headers) {
-		for (Map.Entry<String, List<String>> entry : headers.entrySet()) {
-			String headerName = entry.getKey();
+		headers.forEach((headerName, headerValues) -> {
 			if (HttpHeaders.COOKIE.equalsIgnoreCase(headerName)) {  // RFC 6265
-				String headerValue = StringUtils.collectionToDelimitedString(entry.getValue(), "; ");
+				String headerValue = StringUtils.collectionToDelimitedString(headerValues, "; ");
 				httpRequest.addHeader(headerName, headerValue);
 			}
 			else if (!HTTP.CONTENT_LEN.equalsIgnoreCase(headerName) &&
 					!HTTP.TRANSFER_ENCODING.equalsIgnoreCase(headerName)) {
-				for (String headerValue : entry.getValue()) {
+				for (String headerValue : headerValues) {
 					httpRequest.addHeader(headerName, headerValue);
 				}
 			}
-		}
+		});
 	}
 
 }

spring-web/src/main/java/org/springframework/http/client/Netty4ClientHttpRequest.java

@@ -19,8 +19,6 @@ package org.springframework.http.client;
 import java.io.IOException;
 import java.io.OutputStream;
 import java.net.URI;
-import java.util.List;
-import java.util.Map;
 import java.util.concurrent.ExecutionException;
 
 import io.netty.bootstrap.Bootstrap;
@@ -142,9 +140,7 @@ class Netty4ClientHttpRequest extends AbstractAsyncClientHttpRequest implements
 
 		nettyRequest.headers().set(HttpHeaders.HOST, this.uri.getHost() + ":" + getPort(uri));
 		nettyRequest.headers().set(HttpHeaders.CONNECTION, "close");
-		for (Map.Entry<String, List<String>> entry : headers.entrySet()) {
-			nettyRequest.headers().add(entry.getKey(), entry.getValue());
-		}
+		headers.forEach((headerName, headerValues) -> nettyRequest.headers().add(headerName, headerValues));
 		if (!nettyRequest.headers().contains(HttpHeaders.CONTENT_LENGTH) && this.body.buffer().readableBytes() > 0) {
 			nettyRequest.headers().set(HttpHeaders.CONTENT_LENGTH, this.body.buffer().readableBytes());
 		}

spring-web/src/main/java/org/springframework/http/client/OkHttp3ClientHttpRequestFactory.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -19,8 +19,6 @@ package org.springframework.http.client;
 import java.io.IOException;
 import java.net.MalformedURLException;
 import java.net.URI;
-import java.util.List;
-import java.util.Map;
 import java.util.concurrent.TimeUnit;
 
 import okhttp3.OkHttpClient;
@@ -137,12 +135,11 @@ public class OkHttp3ClientHttpRequestFactory
 				RequestBody.create(contentType, content) : null);
 
 		Request.Builder builder = new Request.Builder().url(uri.toURL()).method(method.name(), body);
-		for (Map.Entry<String, List<String>> entry : headers.entrySet()) {
-			String headerName = entry.getKey();
-			for (String headerValue : entry.getValue()) {
+		headers.forEach((headerName, headerValues) -> {
+			for (String headerValue : headerValues) {
 				builder.addHeader(headerName, headerValue);
 			}
-		}
+		});
 		return builder.build();
 	}
 

spring-web/src/main/java/org/springframework/http/client/SimpleBufferingClientHttpRequest.java

@@ -20,8 +20,6 @@ import java.io.IOException;
 import java.net.HttpURLConnection;
 import java.net.URI;
 import java.net.URISyntaxException;
-import java.util.List;
-import java.util.Map;
 
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpMethod;
@@ -93,19 +91,18 @@ final class SimpleBufferingClientHttpRequest extends AbstractBufferingClientHttp
 	 * @param headers the headers to add
 	 */
 	static void addHeaders(HttpURLConnection connection, HttpHeaders headers) {
-		for (Map.Entry<String, List<String>> entry : headers.entrySet()) {
-			String headerName = entry.getKey();
+		headers.forEach((headerName, headerValues) -> {
 			if (HttpHeaders.COOKIE.equalsIgnoreCase(headerName)) {  // RFC 6265
-				String headerValue = StringUtils.collectionToDelimitedString(entry.getValue(), "; ");
+				String headerValue = StringUtils.collectionToDelimitedString(headerValues, "; ");
 				connection.setRequestProperty(headerName, headerValue);
 			}
 			else {
-				for (String headerValue : entry.getValue()) {
+				for (String headerValue : headerValues) {
 					String actualHeaderValue = headerValue != null ? headerValue : "";
 					connection.addRequestProperty(headerName, actualHeaderValue);
 				}
 			}
-		}
+		});
 	}
 
 }

spring-web/src/main/java/org/springframework/http/server/ServletServerHttpResponse.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -21,7 +21,6 @@ import java.io.OutputStream;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.List;
-import java.util.Map;
 import javax.servlet.http.HttpServletResponse;
 
 import org.springframework.http.HttpHeaders;
@@ -99,12 +98,11 @@ public class ServletServerHttpResponse implements ServerHttpResponse {
 
 	private void writeHeaders() {
 		if (!this.headersWritten) {
-			for (Map.Entry<String, List<String>> entry : this.headers.entrySet()) {
-				String headerName = entry.getKey();
-				for (String headerValue : entry.getValue()) {
+			getHeaders().forEach((headerName, headerValues) -> {
+				for (String headerValue : headerValues) {
 					this.servletResponse.addHeader(headerName, headerValue);
 				}
-			}
+			});
 			// HttpServletResponse exposes some headers as properties: we should include those if not already present
 			if (this.servletResponse.getContentType() == null && this.headers.getContentType() != null) {
 				this.servletResponse.setContentType(this.headers.getContentType().toString());

spring-web/src/main/java/org/springframework/http/server/reactive/DefaultServerHttpRequestBuilder.java

@@ -20,8 +20,6 @@ import java.net.InetSocketAddress;
 import java.net.URI;
 import java.net.URISyntaxException;
 import java.util.LinkedList;
-import java.util.List;
-import java.util.Map;
 import java.util.function.Consumer;
 
 import reactor.core.publisher.Flux;
@@ -80,14 +78,8 @@ class DefaultServerHttpRequestBuilder implements ServerHttpRequest.Builder {
 		this.originalRequest = original;
 	}
 
-	private static <K, V> void copyMultiValueMap(MultiValueMap<K,V> source,
-			MultiValueMap<K,V> destination) {
-
-		for (Map.Entry<K, List<V>> entry : source.entrySet()) {
-			K key = entry.getKey();
-			List<V> values = new LinkedList<>(entry.getValue());
-			destination.put(key, values);
-		}
+	private static <K, V> void copyMultiValueMap(MultiValueMap<K,V> source, MultiValueMap<K,V> target) {
+		source.forEach((key, value) -> target.put(key, new LinkedList<>(value)));
 	}
 
 

spring-web/src/main/java/org/springframework/http/server/reactive/ReactorServerHttpResponse.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -17,8 +17,6 @@
 package org.springframework.http.server.reactive;
 
 import java.io.File;
-import java.util.List;
-import java.util.Map;
 
 import io.netty.buffer.ByteBuf;
 import io.netty.handler.codec.http.HttpResponseStatus;
@@ -85,11 +83,11 @@ class ReactorServerHttpResponse extends AbstractServerHttpResponse implements Ze
 
 	@Override
 	protected void applyHeaders() {
-		for (Map.Entry<String, List<String>> entry : getHeaders().entrySet()) {
-			for (String value : entry.getValue()) {
-				this.response.responseHeaders().add(entry.getKey(), value);
+		getHeaders().forEach((headerName, headerValues) -> {
+			for (String value : headerValues) {
+				this.response.responseHeaders().add(headerName, value);
 			}
-		}
+		});
 	}
 
 	@Override

spring-web/src/main/java/org/springframework/http/server/reactive/ServletServerHttpResponse.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -19,8 +19,6 @@ package org.springframework.http.server.reactive;
 import java.io.IOException;
 import java.io.InputStream;
 import java.nio.charset.Charset;
-import java.util.List;
-import java.util.Map;
 import javax.servlet.AsyncContext;
 import javax.servlet.AsyncEvent;
 import javax.servlet.AsyncListener;
@@ -99,12 +97,11 @@ class ServletServerHttpResponse extends AbstractListenerServerHttpResponse {
 
 	@Override
 	protected void applyHeaders() {
-		for (Map.Entry<String, List<String>> entry : getHeaders().entrySet()) {
-			String headerName = entry.getKey();
-			for (String headerValue : entry.getValue()) {
+		getHeaders().forEach((headerName, headerValues) -> {
+			for (String headerValue : headerValues) {
 				this.response.addHeader(headerName, headerValue);
 			}
-		}
+		});
 		MediaType contentType = getHeaders().getContentType();
 		if (this.response.getContentType() == null && contentType != null) {
 			this.response.setContentType(contentType.toString());

spring-web/src/main/java/org/springframework/http/server/reactive/UndertowServerHttpResponse.java

@@ -21,8 +21,6 @@ import java.io.IOException;
 import java.nio.ByteBuffer;
 import java.nio.channels.FileChannel;
 import java.nio.file.StandardOpenOption;
-import java.util.List;
-import java.util.Map;
 
 import io.undertow.server.HttpServerExchange;
 import io.undertow.server.handlers.Cookie;
@@ -82,10 +80,8 @@ class UndertowServerHttpResponse extends AbstractListenerServerHttpResponse impl
 
 	@Override
 	protected void applyHeaders() {
-		for (Map.Entry<String, List<String>> entry : getHeaders().entrySet()) {
-			HttpString headerName = HttpString.tryFromString(entry.getKey());
-			this.exchange.getResponseHeaders().addAll(headerName, entry.getValue());
-		}
+		getHeaders().forEach((headerName, headerValues) ->
+				this.exchange.getResponseHeaders().addAll(HttpString.tryFromString(headerName), headerValues));
 	}
 
 	@Override

spring-web/src/main/java/org/springframework/web/accept/ContentNegotiationManagerFactoryBean.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -21,7 +21,6 @@ import java.util.HashMap;
 import java.util.List;
 import java.util.Locale;
 import java.util.Map;
-import java.util.Map.Entry;
 import java.util.Properties;
 import javax.servlet.ServletContext;
 
@@ -160,11 +159,11 @@ public class ContentNegotiationManagerFactoryBean
 	 */
 	public void setMediaTypes(Properties mediaTypes) {
 		if (!CollectionUtils.isEmpty(mediaTypes)) {
-			for (Entry<Object, Object> entry : mediaTypes.entrySet()) {
-				String extension = ((String)entry.getKey()).toLowerCase(Locale.ENGLISH);
-				MediaType mediaType = MediaType.valueOf((String) entry.getValue());
+			mediaTypes.forEach((key, value) -> {
+				String extension = ((String) key).toLowerCase(Locale.ENGLISH);
+				MediaType mediaType = MediaType.valueOf((String) value);
 				this.mediaTypes.put(extension, mediaType);
-			}
+			});
 		}
 	}
 

spring-web/src/main/java/org/springframework/web/accept/MappingMediaTypeFileExtensionResolver.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -22,7 +22,6 @@ import java.util.LinkedList;
 import java.util.List;
 import java.util.Locale;
 import java.util.Map;
-import java.util.Map.Entry;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ConcurrentMap;
 
@@ -43,11 +42,9 @@ import org.springframework.util.MultiValueMap;
  */
 public class MappingMediaTypeFileExtensionResolver implements MediaTypeFileExtensionResolver {
 
-	private final ConcurrentMap<String, MediaType> mediaTypes =
-			new ConcurrentHashMap<>(64);
+	private final ConcurrentMap<String, MediaType> mediaTypes = new ConcurrentHashMap<>(64);
 
-	private final MultiValueMap<MediaType, String> fileExtensions =
-			new LinkedMultiValueMap<>();
+	private final MultiValueMap<MediaType, String> fileExtensions = new LinkedMultiValueMap<>();
 
 	private final List<String> allFileExtensions = new LinkedList<>();
 
@@ -57,13 +54,12 @@ public class MappingMediaTypeFileExtensionResolver implements MediaTypeFileExten
 	 */
 	public MappingMediaTypeFileExtensionResolver(@Nullable Map<String, MediaType> mediaTypes) {
 		if (mediaTypes != null) {
-			for (Entry<String, MediaType> entries : mediaTypes.entrySet()) {
-				String extension = entries.getKey().toLowerCase(Locale.ENGLISH);
-				MediaType mediaType = entries.getValue();
-				this.mediaTypes.put(extension, mediaType);
-				this.fileExtensions.add(mediaType, extension);
-				this.allFileExtensions.add(extension);
-			}
+			mediaTypes.forEach((extension, mediaType) -> {
+				String lowerCaseExtension = extension.toLowerCase(Locale.ENGLISH);
+				this.mediaTypes.put(lowerCaseExtension, mediaType);
+				this.fileExtensions.add(mediaType, lowerCaseExtension);
+				this.allFileExtensions.add(lowerCaseExtension);
+			});
 		}
 	}
 
@@ -91,7 +87,7 @@ public class MappingMediaTypeFileExtensionResolver implements MediaTypeFileExten
 	@Override
 	public List<String> resolveFileExtensions(MediaType mediaType) {
 		List<String> fileExtensions = this.fileExtensions.get(mediaType);
-		return (fileExtensions != null) ? fileExtensions : Collections.emptyList();
+		return (fileExtensions != null ? fileExtensions : Collections.emptyList());
 	}
 
 	@Override

spring-web/src/main/java/org/springframework/web/bind/WebDataBinder.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -315,9 +315,7 @@ public class WebDataBinder extends DataBinder {
 	 * @see #setBindEmptyMultipartFiles
 	 */
 	protected void bindMultipart(Map<String, List<MultipartFile>> multipartFiles, MutablePropertyValues mpvs) {
-		for (Map.Entry<String, List<MultipartFile>> entry : multipartFiles.entrySet()) {
-			String key = entry.getKey();
-			List<MultipartFile> values = entry.getValue();
+		multipartFiles.forEach((key, values) -> {
 			if (values.size() == 1) {
 				MultipartFile value = values.get(0);
 				if (isBindEmptyMultipartFiles() || !value.isEmpty()) {
@@ -327,7 +325,7 @@ public class WebDataBinder extends DataBinder {
 			else {
 				mpvs.add(key, values);
 			}
-		}
+		});
 	}
 
 }

spring-web/src/main/java/org/springframework/web/bind/support/WebRequestDataBinder.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,8 +16,6 @@
 
 package org.springframework.web.bind.support;
 
-import java.util.List;
-import java.util.Map;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.Part;
 
@@ -141,17 +139,17 @@ public class WebRequestDataBinder extends WebDataBinder {
 			for (Part part : request.getParts()) {
 				map.add(part.getName(), part);
 			}
-			for (Map.Entry<String, List<Part>> entry: map.entrySet()) {
-				if (entry.getValue().size() == 1) {
-					Part part = entry.getValue().get(0);
+			map.forEach((key, values) -> {
+				if (values.size() == 1) {
+					Part part = values.get(0);
 					if (isBindEmptyMultipartFiles() || part.getSize() > 0) {
-						mpvs.add(entry.getKey(), part);
+						mpvs.add(key, part);
 					}
 				}
 				else {
-					mpvs.add(entry.getKey(), entry.getValue());
+					mpvs.add(key, values);
 				}
-			}
+			});
 		}
 		catch (Exception ex) {
 			throw new MultipartException("Failed to get request parts", ex);

spring-web/src/main/java/org/springframework/web/client/RestTemplate.java

@@ -912,9 +912,7 @@ public class RestTemplate extends InterceptingHttpAccessor implements RestOperat
 				HttpHeaders httpHeaders = httpRequest.getHeaders();
 				HttpHeaders requestHeaders = this.requestEntity.getHeaders();
 				if (!requestHeaders.isEmpty()) {
-					for (Map.Entry<String, List<String>> entry : requestHeaders.entrySet()) {
-						httpHeaders.put(entry.getKey(), new LinkedList<>(entry.getValue()));
-					}
+					requestHeaders.forEach((key, values) -> httpHeaders.put(key, new LinkedList<>(values)));
 				}
 				if (httpHeaders.getContentLength() < 0) {
 					httpHeaders.setContentLength(0L);
@@ -933,9 +931,7 @@ public class RestTemplate extends InterceptingHttpAccessor implements RestOperat
 								(GenericHttpMessageConverter<Object>) messageConverter;
 						if (genericConverter.canWrite(requestBodyType, requestBodyClass, requestContentType)) {
 							if (!requestHeaders.isEmpty()) {
-								for (Map.Entry<String, List<String>> entry : requestHeaders.entrySet()) {
-									httpHeaders.put(entry.getKey(), new LinkedList<>(entry.getValue()));
-								}
+								requestHeaders.forEach((key, values) -> httpHeaders.put(key, new LinkedList<>(values)));
 							}
 							if (logger.isDebugEnabled()) {
 								if (requestContentType != null) {
@@ -953,9 +949,7 @@ public class RestTemplate extends InterceptingHttpAccessor implements RestOperat
 					}
 					else if (messageConverter.canWrite(requestBodyClass, requestContentType)) {
 						if (!requestHeaders.isEmpty()) {
-							for (Map.Entry<String, List<String>> entry : requestHeaders.entrySet()) {
-								httpHeaders.put(entry.getKey(), new LinkedList<>(entry.getValue()));
-							}
+							requestHeaders.forEach((key, values) -> httpHeaders.put(key, new LinkedList<>(values)));
 						}
 						if (logger.isDebugEnabled()) {
 							if (requestContentType != null) {

spring-web/src/main/java/org/springframework/web/method/annotation/RequestParamMapMethodArgumentResolver.java

@@ -64,20 +64,20 @@ public class RequestParamMapMethodArgumentResolver implements HandlerMethodArgum
 		Map<String, String[]> parameterMap = webRequest.getParameterMap();
 		if (MultiValueMap.class.isAssignableFrom(paramType)) {
 			MultiValueMap<String, String> result = new LinkedMultiValueMap<>(parameterMap.size());
-			for (Map.Entry<String, String[]> entry : parameterMap.entrySet()) {
-				for (String value : entry.getValue()) {
-					result.add(entry.getKey(), value);
+			parameterMap.forEach((key, values) -> {
+				for (String value : values) {
+					result.add(key, value);
 				}
-			}
+			});
 			return result;
 		}
 		else {
 			Map<String, String> result = new LinkedHashMap<>(parameterMap.size());
-			for (Map.Entry<String, String[]> entry : parameterMap.entrySet()) {
-				if (entry.getValue().length > 0) {
-					result.put(entry.getKey(), entry.getValue()[0]);
+			parameterMap.forEach((key, values) -> {
+				if (values.length > 0) {
+					result.put(key, values[0]);
 				}
-			}
+			});
 			return result;
 		}
 	}

spring-web/src/main/java/org/springframework/web/util/HierarchicalUriComponents.java

@@ -26,7 +26,6 @@ import java.util.Arrays;
 import java.util.Collections;
 import java.util.Iterator;
 import java.util.List;
-import java.util.Map;
 
 import org.springframework.lang.NonNull;
 import org.springframework.lang.Nullable;
@@ -151,9 +150,7 @@ final class HierarchicalUriComponents extends UriComponents {
 	public String getQuery() {
 		if (!this.queryParams.isEmpty()) {
 			StringBuilder queryBuilder = new StringBuilder();
-			for (Map.Entry<String, List<String>> entry : this.queryParams.entrySet()) {
-				String name = entry.getKey();
-				List<String> values = entry.getValue();
+			this.queryParams.forEach((name, values) -> {
 				if (CollectionUtils.isEmpty(values)) {
 					if (queryBuilder.length() != 0) {
 						queryBuilder.append('&');
@@ -171,7 +168,7 @@ final class HierarchicalUriComponents extends UriComponents {
 						}
 					}
 				}
-			}
+			});
 			return queryBuilder.toString();
 		}
 		else {
@@ -216,14 +213,14 @@ final class HierarchicalUriComponents extends UriComponents {
 	private MultiValueMap<String, String> encodeQueryParams(Charset charset) {
 		int size = this.queryParams.size();
 		MultiValueMap<String, String> result = new LinkedMultiValueMap<>(size);
-		for (Map.Entry<String, List<String>> entry : this.queryParams.entrySet()) {
-			String name = encodeUriComponent(entry.getKey(), charset, Type.QUERY_PARAM);
-			List<String> values = new ArrayList<>(entry.getValue().size());
-			for (String value : entry.getValue()) {
-				values.add(encodeUriComponent(value, charset, Type.QUERY_PARAM));
-			}
-			result.put(name, values);
-		}
+		this.queryParams.forEach((key, values) -> {
+			String name = encodeUriComponent(key, charset, Type.QUERY_PARAM);
+			List<String> encodedValues = new ArrayList<>(values.size());
+			for (String value : values) {
+				encodedValues.add(encodeUriComponent(value, charset, Type.QUERY_PARAM));
+			}
+			result.put(name, encodedValues);
+		});
 		return result;
 	}
 
@@ -298,12 +295,12 @@ final class HierarchicalUriComponents extends UriComponents {
 		verifyUriComponent(this.userInfo, Type.USER_INFO);
 		verifyUriComponent(this.host, getHostType());
 		this.path.verify();
-		for (Map.Entry<String, List<String>> entry : queryParams.entrySet()) {
-			verifyUriComponent(entry.getKey(), Type.QUERY_PARAM);
-			for (String value : entry.getValue()) {
+		this.queryParams.forEach((key, values) -> {
+			verifyUriComponent(key, Type.QUERY_PARAM);
+			for (String value : values) {
 				verifyUriComponent(value, Type.QUERY_PARAM);
 			}
-		}
+		});
 		verifyUriComponent(getFragment(), Type.FRAGMENT);
 	}
 
@@ -360,15 +357,15 @@ final class HierarchicalUriComponents extends UriComponents {
 	private MultiValueMap<String, String> expandQueryParams(UriTemplateVariables variables) {
 		int size = this.queryParams.size();
 		MultiValueMap<String, String> result = new LinkedMultiValueMap<>(size);
-		variables = new QueryUriTemplateVariables(variables);
-		for (Map.Entry<String, List<String>> entry : this.queryParams.entrySet()) {
-			String name = expandUriComponent(entry.getKey(), variables);
-			List<String> values = new ArrayList<>(entry.getValue().size());
-			for (String value : entry.getValue()) {
-				values.add(expandUriComponent(value, variables));
-			}
-			result.put(name, values);
-		}
+		UriTemplateVariables queryVariables = new QueryUriTemplateVariables(variables);
+		this.queryParams.forEach((key, values) -> {
+			String name = expandUriComponent(key, queryVariables);
+			List<String> expandedValues = new ArrayList<>(values.size());
+			for (String value : values) {
+				expandedValues.add(expandUriComponent(value, queryVariables));
+			}
+			result.put(name, expandedValues);
+		});
 		return result;
 	}
 

spring-web/src/main/java/org/springframework/web/util/UrlPathHelper.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -20,7 +20,6 @@ import java.net.URLDecoder;
 import java.nio.charset.UnsupportedCharsetException;
 import java.util.LinkedHashMap;
 import java.util.Map;
-import java.util.Map.Entry;
 import java.util.Properties;
 import javax.servlet.ServletContext;
 import javax.servlet.http.HttpServletRequest;
@@ -544,9 +543,7 @@ public class UrlPathHelper {
 		}
 		else {
 			Map<String, String> decodedVars = new LinkedHashMap<>(vars.size());
-			for (Entry<String, String> entry : vars.entrySet()) {
-				decodedVars.put(entry.getKey(), decodeInternal(request, entry.getValue()));
-			}
+			vars.forEach((key, value) -> decodedVars.put(key, decodeInternal(request, value)));
 			return decodedVars;
 		}
 	}

spring-webflux/src/main/java/org/springframework/web/reactive/function/BodyExtractors.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -36,7 +36,6 @@ import org.springframework.http.codec.HttpMessageReader;
 import org.springframework.http.codec.multipart.Part;
 import org.springframework.http.server.reactive.ServerHttpRequest;
 import org.springframework.http.server.reactive.ServerHttpResponse;
-import org.springframework.util.Assert;
 import org.springframework.util.MultiValueMap;
 
 /**
@@ -65,7 +64,6 @@ public abstract class BodyExtractors {
 	 * @return a {@code BodyExtractor} that reads a mono
 	 */
 	public static <T> BodyExtractor<Mono<T>, ReactiveHttpInputMessage> toMono(Class<? extends T> elementClass) {
-		Assert.notNull(elementClass, "'elementClass' must not be null");
 		return toMono(ResolvableType.forClass(elementClass));
 	}
 
@@ -87,12 +85,10 @@ public abstract class BodyExtractors {
 	public static <T> BodyExtractor<Mono<T>, ReactiveHttpInputMessage> toMono(
 			ParameterizedTypeReference<T> typeReference) {
 
-		Assert.notNull(typeReference, "'typeReference' must not be null");
 		return toMono(ResolvableType.forType(typeReference.getType()));
 	}
 
 	static <T> BodyExtractor<Mono<T>, ReactiveHttpInputMessage> toMono(ResolvableType elementType) {
-		Assert.notNull(elementType, "'elementType' must not be null");
 		return (inputMessage, context) -> readWithMessageReaders(inputMessage, context,
 				elementType,
 				(HttpMessageReader<T> reader) -> {
@@ -117,7 +113,6 @@ public abstract class BodyExtractors {
 	 * @return a {@code BodyExtractor} that reads a flux
 	 */
 	public static <T> BodyExtractor<Flux<T>, ReactiveHttpInputMessage> toFlux(Class<? extends T> elementClass) {
-		Assert.notNull(elementClass, "'elementClass' must not be null");
 		return toFlux(ResolvableType.forClass(elementClass));
 	}
 
@@ -139,13 +134,11 @@ public abstract class BodyExtractors {
 	public static <T> BodyExtractor<Flux<T>, ReactiveHttpInputMessage> toFlux(
 			ParameterizedTypeReference<T> typeReference) {
 
-		Assert.notNull(typeReference, "'typeReference' must not be null");
 		return toFlux(ResolvableType.forType(typeReference.getType()));
 	}
 
 	@SuppressWarnings("unchecked")
 	static <T> BodyExtractor<Flux<T>, ReactiveHttpInputMessage> toFlux(ResolvableType elementType) {
-		Assert.notNull(elementType, "'elementType' must not be null");
 		return (inputMessage, context) -> readWithMessageReaders(inputMessage, context,
 				elementType,
 				(HttpMessageReader<T> reader) -> {

spring-webflux/src/main/java/org/springframework/web/reactive/function/BodyInserters.java

@@ -17,7 +17,6 @@
 package org.springframework.web.reactive.function;
 
 import java.util.List;
-import java.util.Map;
 import java.util.Optional;
 import java.util.stream.Collectors;
 
@@ -87,7 +86,6 @@ public abstract class BodyInserters {
 	 * @return a {@code BodyInserter} that writes a single object
 	 */
 	public static <T> BodyInserter<T, ReactiveHttpOutputMessage> fromObject(T body) {
-		Assert.notNull(body, "'body' must not be null");
 		return bodyInserterFor(Mono.just(body), ResolvableType.forInstance(body));
 	}
 
@@ -106,8 +104,6 @@ public abstract class BodyInserters {
 	public static <T, P extends Publisher<T>> BodyInserter<P, ReactiveHttpOutputMessage> fromPublisher(
 			P publisher, Class<T> elementClass) {
 
-		Assert.notNull(publisher, "'publisher' must not be null");
-		Assert.notNull(elementClass, "'elementClass' must not be null");
 		return bodyInserterFor(publisher, ResolvableType.forClass(elementClass));
 	}
 
@@ -126,8 +122,6 @@ public abstract class BodyInserters {
 	public static <T, P extends Publisher<T>> BodyInserter<P, ReactiveHttpOutputMessage> fromPublisher(
 			P publisher, ParameterizedTypeReference<T> typeReference) {
 
-		Assert.notNull(publisher, "'publisher' must not be null");
-		Assert.notNull(typeReference, "'typeReference' must not be null");
 		return bodyInserterFor(publisher, ResolvableType.forType(typeReference.getType()));
 	}
 
@@ -140,7 +134,6 @@ public abstract class BodyInserters {
 	 * @return a {@code BodyInserter} that writes a {@code Publisher}
 	 */
 	public static <T extends Resource> BodyInserter<T, ReactiveHttpOutputMessage> fromResource(T resource) {
-		Assert.notNull(resource, "'resource' must not be null");
 		return (outputMessage, context) -> {
 			Mono<T> inputStream = Mono.just(resource);
 			HttpMessageWriter<Resource> messageWriter = resourceHttpMessageWriter(context);
@@ -180,7 +173,6 @@ public abstract class BodyInserters {
 	public static <T, S extends Publisher<ServerSentEvent<T>>> BodyInserter<S, ServerHttpResponse> fromServerSentEvents(
 			S eventsPublisher) {
 
-		Assert.notNull(eventsPublisher, "'eventsPublisher' must not be null");
 		return (serverResponse, context) -> {
 			HttpMessageWriter<ServerSentEvent<T>> messageWriter =
 					findMessageWriter(context, SERVER_SIDE_EVENT_TYPE, MediaType.TEXT_EVENT_STREAM);
@@ -208,7 +200,6 @@ public abstract class BodyInserters {
 	 * @return the inserter that allows adding more form data
 	 */
 	public static FormInserter<String> fromFormData(MultiValueMap<String, String> formData) {
-		Assert.notNull(formData, "'formData' must not be null");
 		return new DefaultFormInserter().with(formData);
 	}
 
@@ -389,7 +380,7 @@ public abstract class BodyInserters {
 		 * @param value the value to be added
 		 * @return this inserter for adding more parts
 		 */
-		FormInserter<T> with(String key, @Nullable T value);
+		FormInserter<T> with(String key, T value);
 
 		/**
 		 * Adds the specified values to the form.
@@ -435,11 +426,6 @@ public abstract class BodyInserters {
 
 		private final MultiValueMap<String, String> data = new LinkedMultiValueMap<>();
 
-
-		public DefaultFormInserter() {
-		}
-
-
 		@Override
 		public FormInserter<String> with(String key, @Nullable String value) {
 			this.data.add(key, value);
@@ -467,14 +453,8 @@ public abstract class BodyInserters {
 
 		private final MultipartBodyBuilder builder = new MultipartBodyBuilder();
 
-
-		public DefaultMultipartInserter() {
-		}
-
-
 		@Override
-		public MultipartInserter with(String key, @Nullable Object value) {
-			Assert.notNull(value, "'value' must not be null");
+		public MultipartInserter with(String key, Object value) {
 			this.builder.part(key, value);
 			return this;
 		}
@@ -486,26 +466,25 @@ public abstract class BodyInserters {
 
 		@SuppressWarnings("unchecked")
 		private MultipartInserter withInternal(MultiValueMap<String, ?> values) {
-			Assert.notNull(values, "'values' must not be null");
-			for (Map.Entry<String, ? extends List<?>> entry : values.entrySet()) {
-				for (Object value : entry.getValue()) {
-					this.builder.part(entry.getKey(), value);
+			values.forEach((key, valueList) -> {
+				for (Object value : valueList) {
+					this.builder.part(key, value);
 				}
-			}
+			});
 			return this;
 		}
 
 		@Override
-		public <T, P extends Publisher<T>> MultipartInserter withPublisher(String name,
-				P publisher, Class<T> elementClass) {
+		public <T, P extends Publisher<T>> MultipartInserter withPublisher(
+				String name, P publisher, Class<T> elementClass) {
 
 			this.builder.asyncPart(name, publisher, elementClass);
 			return this;
 		}
 
 		@Override
-		public <T, P extends Publisher<T>> MultipartInserter withPublisher(String name,
-				P publisher, ParameterizedTypeReference<T> typeReference) {
+		public <T, P extends Publisher<T>> MultipartInserter withPublisher(
+				String name, P publisher, ParameterizedTypeReference<T> typeReference) {
 
 			this.builder.asyncPart(name, publisher, typeReference);
 			return this;

spring-webmvc/src/main/java/org/springframework/web/servlet/handler/AbstractHandlerMethodMapping.java

@@ -245,11 +245,10 @@ public abstract class AbstractHandlerMethodMapping<T> extends AbstractHandlerMap
 			if (logger.isDebugEnabled()) {
 				logger.debug(methods.size() + " request handler methods found on " + userType + ": " + methods);
 			}
-			for (Map.Entry<Method, T> entry : methods.entrySet()) {
-				Method invocableMethod = AopUtils.selectInvocableMethod(entry.getKey(), userType);
-				T mapping = entry.getValue();
+			methods.forEach((method, mapping) -> {
+				Method invocableMethod = AopUtils.selectInvocableMethod(method, userType);
 				registerHandlerMethod(handler, invocableMethod, mapping);
-			}
+			});
 		}
 	}
 

spring-webmvc/src/main/java/org/springframework/web/servlet/mvc/method/annotation/ExceptionHandlerExceptionResolver.java

@@ -23,7 +23,6 @@ import java.util.Collections;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
-import java.util.Map.Entry;
 import java.util.concurrent.ConcurrentHashMap;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
@@ -470,7 +469,7 @@ public class ExceptionHandlerExceptionResolver extends AbstractHandlerMethodExce
 			}
 		}
 
-		for (Entry<ControllerAdviceBean, ExceptionHandlerMethodResolver> entry : this.exceptionHandlerAdviceCache.entrySet()) {
+		for (Map.Entry<ControllerAdviceBean, ExceptionHandlerMethodResolver> entry : this.exceptionHandlerAdviceCache.entrySet()) {
 			ControllerAdviceBean advice = entry.getKey();
 			if (advice.isApplicableToBeanType(handlerType)) {
 				ExceptionHandlerMethodResolver resolver = entry.getValue();

spring-webmvc/src/main/java/org/springframework/web/servlet/resource/ResourceHttpRequestHandler.java

@@ -700,10 +700,9 @@ public class ResourceHttpRequestHandler extends WebContentGenerator
 		}
 		if (resource instanceof HttpResource) {
 			HttpHeaders resourceHeaders = ((HttpResource) resource).getResponseHeaders();
-			for (Map.Entry<String, List<String>> entry : resourceHeaders.entrySet()) {
-				String headerName = entry.getKey();
+			resourceHeaders.forEach((headerName, headerValues) -> {
 				boolean first = true;
-				for (String headerValue : entry.getValue()) {
+				for (String headerValue : headerValues) {
 					if (first) {
 						response.setHeader(headerName, headerValue);
 					}
@@ -712,7 +711,7 @@ public class ResourceHttpRequestHandler extends WebContentGenerator
 					}
 					first = false;
 				}
-			}
+			});
 		}
 		response.setHeader(HttpHeaders.ACCEPT_RANGES, "bytes");
 	}

spring-websocket/src/main/java/org/springframework/web/socket/WebSocketExtension.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -119,12 +119,7 @@ public class WebSocketExtension {
 	public String toString() {
 		StringBuilder str = new StringBuilder();
 		str.append(this.name);
-		for (Map.Entry<String, String> entry : this.parameters.entrySet()) {
-			str.append(';');
-			str.append(entry.getKey());
-			str.append('=');
-			str.append(entry.getValue());
-		}
+		this.parameters.forEach((key, value) -> str.append(';').append(key).append('=').append(value));
 		return str.toString();
 	}
 

spring-websocket/src/main/java/org/springframework/web/socket/adapter/jetty/WebSocketToJettyExtensionConfigAdapter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2013 the original author or authors.
+ * Copyright 2002-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,8 +16,6 @@
 
 package org.springframework.web.socket.adapter.jetty;
 
-import java.util.Map;
-
 import org.eclipse.jetty.websocket.api.extensions.ExtensionConfig;
 
 import org.springframework.web.socket.WebSocketExtension;
@@ -30,8 +28,7 @@ public class WebSocketToJettyExtensionConfigAdapter extends ExtensionConfig {
 
 	public WebSocketToJettyExtensionConfigAdapter(WebSocketExtension extension) {
 		super(extension.getName());
-		for (Map.Entry<String,String> p : extension.getParameters().entrySet()) {
-			super.setParameter(p.getKey(), p.getValue());
-		}
+		extension.getParameters().forEach(super::setParameter);
 	}
+
 }

spring-websocket/src/main/java/org/springframework/web/socket/server/standard/GlassFishRequestUpgradeStrategy.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -18,8 +18,6 @@ package org.springframework.web.socket.server.standard;
 
 import java.io.IOException;
 import java.lang.reflect.Constructor;
-import java.util.List;
-import java.util.Map;
 import javax.servlet.ServletException;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
@@ -67,9 +65,7 @@ public class GlassFishRequestUpgradeStrategy extends AbstractTyrusRequestUpgrade
 		handler.preInit(upgradeInfo, servletWriter, request.getUserPrincipal() != null);
 
 		response.setStatus(upgradeResponse.getStatus());
-		for (Map.Entry<String, List<String>> entry : upgradeResponse.getHeaders().entrySet()) {
-			response.addHeader(entry.getKey(), Utils.getHeaderFromList(entry.getValue()));
-		}
+		upgradeResponse.getHeaders().forEach((key, value) -> response.addHeader(key, Utils.getHeaderFromList(value)));
 		response.flushBuffer();
 	}
 

spring-websocket/src/main/java/org/springframework/web/socket/server/standard/WebLogicRequestUpgradeStrategy.java

@@ -19,8 +19,6 @@ package org.springframework.web.socket.server.standard;
 import java.io.IOException;
 import java.lang.reflect.Constructor;
 import java.lang.reflect.Method;
-import java.util.List;
-import java.util.Map;
 import javax.servlet.AsyncContext;
 import javax.servlet.ServletContext;
 import javax.servlet.ServletException;
@@ -63,9 +61,7 @@ public class WebLogicRequestUpgradeStrategy extends AbstractTyrusRequestUpgradeS
 			UpgradeInfo upgradeInfo, TyrusUpgradeResponse upgradeResponse) throws IOException, ServletException {
 
 		response.setStatus(upgradeResponse.getStatus());
-		for (Map.Entry<String, List<String>> entry : upgradeResponse.getHeaders().entrySet()) {
-			response.addHeader(entry.getKey(), Utils.getHeaderFromList(entry.getValue()));
-		}
+		upgradeResponse.getHeaders().forEach((key, value) -> response.addHeader(key, Utils.getHeaderFromList(value)));
 
 		AsyncContext asyncContext = request.startAsync();
 		asyncContext.setTimeout(-1L);

spring-websocket/src/main/java/org/springframework/web/socket/sockjs/client/JettyXhrTransport.java

@@ -20,8 +20,6 @@ import java.io.ByteArrayOutputStream;
 import java.net.URI;
 import java.nio.ByteBuffer;
 import java.util.Enumeration;
-import java.util.List;
-import java.util.Map;
 
 import org.eclipse.jetty.client.HttpClient;
 import org.eclipse.jetty.client.api.ContentResponse;
@@ -161,11 +159,11 @@ public class JettyXhrTransport extends AbstractXhrTransport implements Lifecycle
 
 
 	private static void addHttpHeaders(Request request, HttpHeaders headers) {
-		for (Map.Entry<String, List<String>> entry : headers.entrySet()) {
-			for (String value : entry.getValue()) {
-				request.header(entry.getKey(), value);
+		headers.forEach((key, values) -> {
+			for (String value : values) {
+				request.header(key, value);
 			}
-		}
+		});
 	}
 
 	private static HttpHeaders toHttpHeaders(HttpFields httpFields) {

spring-websocket/src/main/java/org/springframework/web/socket/sockjs/client/UndertowXhrTransport.java

@@ -21,7 +21,6 @@ import java.io.IOException;
 import java.net.URI;
 import java.nio.ByteBuffer;
 import java.util.List;
-import java.util.Map;
 import java.util.concurrent.CopyOnWriteArrayList;
 import java.util.concurrent.CountDownLatch;
 
@@ -171,11 +170,11 @@ public class UndertowXhrTransport extends AbstractXhrTransport {
 
 	private static void addHttpHeaders(ClientRequest request, HttpHeaders headers) {
 		HeaderMap headerMap = request.getRequestHeaders();
-		for (Map.Entry<String, List<String>> entry : headers.entrySet()) {
-			for (String value : entry.getValue()) {
-				headerMap.add(HttpString.tryFromString(entry.getKey()), value);
+		headers.forEach((key, values) -> {
+			for (String value : values) {
+				headerMap.add(HttpString.tryFromString(key), value);
 			}
-		}
+		});
 	}
 
 	private ClientCallback<ClientExchange> createReceiveCallback(final TransportRequest transportRequest,